This invention relates to water dispersible polymeric films, to processes for the film preparation and materials for use in forming the water dispersible polymeric films.
In recent times, community, public and private organizational recycling of paper products has grown tremendously, including growth in the types and variety of papers subject to repulping, which is the primary form of paper recycling. However with the expansion of the nature and type of paper products subject to repulping operations problems have arisen from contamination of the pulp feedstream by materials which are not readily subject to repulping. These contaminants are often difficult to remove either before or during the repulping operation. For example, significant amounts of plastic films are used in conjunction with envelopes, paper mailings, magazine and newspaper inserts, and packaging, either as a packaging film or as a tape product applied to a package, or the like. Paper products used with these plastic films are generally not accepted by most recyclers, and entire lots of collected materials containing such plastic contaminants are sometimes rejected by the repulper as unprocessable hindering community attempts at reducing the need to landfill.
A potential solution to this problem would be by using water soluble or dispersible polymer films in applications that are most likely to cause problems with repulping of recycled materials. There are numerous commercially available water soluble or dispersible film forming polymers, the most common of which is polyvinyl alcohol, and the use of these water soluble polymer films would be acceptable in many applications. However, generally, these water soluble polymers are so sensitive to water that their use is limited, particularly in high humidity and high temperature locations. Suggested solutions to this water and humidity sensitivity problem include protecting the water soluble films with a thin surface layer, such as disclosed in U.S. Pat. No. 3,705,659 (which proposes using a thin, photodegradable, polyethylene film on both faces of a water soluble film); U.S. Pat. No. 4,372,311 (where a water soluble polymer is coated with a water-insoluble, biodegradable polymer); U.S. Pat. No. 5,200,247(which blends in a alkanoyl polymer with polyvinyl alcohol, which allegedly improves water resistance of the water soluble film while enhancing biodegradability); and U.S. Pat. No. 4,692,494 (which blends in polyacrylic acid with polyvinyl alcohol to provide the water soluble film with more humidity resistance). The coated or coextruded films, while providing humidity and water resistance, can not be readily repulped. The above polymer blends solutions do not necessarily provide the amount of humidity resistance or moisture resistance required while also providing a repulpable film. There remains a distinct need for further options in providing a water dispersible or repulpable film product that is also more resistant to water than conventional water soluble polymer films. There is particularly a need for a repulpable film that disintegrates into small enough particles such that the particles do not cause problems when the pulp is formed into new paper stock.